BEC/Fraud: Generic scam attempt to undisclosed recipients

 1name: "BEC/Fraud: Generic scam attempt to undisclosed recipients"
 2description: |
 3    Detects potential generic scams by analyzing text within the email body and other suspicious signals.
 4type: "rule"
 5severity: "low"
 6source: |
 7  type.inbound
 8  
 9  // undisclosed recipients
10  and any([recipients.to, recipients.bcc, recipients.cc],
11          any(., .display_name =~ "Undisclosed recipients")
12  )
13  
14  // mismatched sender (from) and Reply-to
15  and (
16    length(headers.reply_to) > 0
17    and all(headers.reply_to,
18            .email.domain.root_domain != sender.email.domain.root_domain
19    )
20  )
21  
22  // generic recipient
23  and any(ml.nlu_classifier(body.current_thread.text).entities,
24          .name == "recipient" and regex.icontains(.text, "(sir|madam)")
25  )
26  
27  // request made
28  and any(ml.nlu_classifier(body.current_thread.text).entities,
29          .name == "request"
30  )
31  
32  // not a bec scam
33  and all(ml.nlu_classifier(body.current_thread.text).intents, .name != "bec")
34  
35  // negate highly trusted sender domains unless they fail DMARC authentication
36  and not (
37    sender.email.domain.root_domain in $high_trust_sender_root_domains
38    and coalesce(headers.auth_summary.dmarc.pass, false)
39  )  
40attack_types:
41  - "BEC/Fraud"
42tactics_and_techniques:
43  - "Social engineering"
44detection_methods:
45  - "Content analysis"
46  - "Header analysis"
47  - "Natural Language Understanding"
48  - "Sender analysis"
49id: "5dac401f-d3c1-5092-aba4-58ab597c702b"